st: seeking suggestions on how to illustrate data

This is not a Stata question per se, but I hope the
solution is something I can do in Stata.
I have a dataset consisting of 5 overlapping cohorts
of patients. Basically, every 6 mos data is collected
on every (diabetes) patient seen at a network of clinics.
I have the first 2.5 years (there will be another 2.5).
There is a lot of overlap between the 5 cohorts. There are
about 10k obs per cohort, and each "snapshot" includes about
80% of patients that are seen in another cohort. I would
like to illustrate this somehow, because the amount of
overlap is of interest. The figure should also capture the
time trend (ie, a Venn diagram wouldn't really do it).
I imagine some sort of figure with 5 bars, each with height
representing the # obs and divided somehow to represent the
number of patients in that cohort that were seen in other
cohorts. Ideally - and this is the hard part - the figure
would also indicate somehow the number of times patients in
that cohort were seen in other cohorts.
I'm just fishing here for ideas - I've never seen anything
like this, but maybe some of our talented listers have?
thanks for any ideas,
Jeph
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